Pinouts

Power Pins

The sensor on the breakout requires between a 2.7V and 5.5V, and can be easily used with most microcontrollers from an Arduino to a Feather or something else.

  • Vcc - this is the power pin.  To power the board, give it the same power as the logic level of your microcontroller - e.g. for a 5V micro like Arduino, use 5V
  • GND - common ground for power and logic

I2C Logic Pins

  • SCL - I2C clock pin, connect to your microcontrollers I2C clock line. The logic level is the same as Vcc and it has a 10K pullup already on it.
  • SDA - I2C data pin, connect to your microcontrollers I2C data line. The logic level is the same as Vcc. and it has a 10K pullup already on it.
  • STEMMA QT - These connectors allow you to connectors to dev boards with STEMMA QT connectors or to other things with various associated accessories

Resistor Pins

  • RL is the Low Terminal of the potentiometer, often connected to ground.
  • RW is the wiper of the potentiometer. As the wiper value is adjusted via I2C, the resistance between RW and RL/RH changes 
  • RH is the High Terminal of the potentiometer, often connected to your high voltage source.
  • V+ is the wiper bias pin and is used to bias the gates of the MOSFETs that are responsible for changing the resistance between RW and RH or RL. If the voltage at RH is higher than VCCV+ must be at the same or higher voltage than RH. By default this is connected with a jumper to RH but you can cut the solder jumper and wire it directly

Extra Pins

  • A0 and A1 - These are the address select pins.

Since you can only have one device with a given address on an I2C bus, there must be a way to adjust the address if you want to put more than one DS3502 on a shared I2C bus. The A0/A1 pins set the bottom two bits of the I2C address. There are pull-down resistors on the board so connect them to VDD, you can solder the back jumpers or wire them on a breadboard, to set the bits to '1'. They are read on power up, so de-power and re-power to reset the address

The default address is 0x28 and the address can be calculated by 'adding' the A0/A1 to the base of 0x28

A0 sets the lowest bit with a value of 1, and A1 sets the middle bit with a value of 2. The final address is 0x28 + A1 + A0.

  • So for example if only A0 is tied to VDD, the address is 0x28 + 1 = 0x29
  • If only A1 is tied to VDD, the address is 0x28 + 2 = 0x2A
  • If A1 is tied to VDD and A0 is tied to VDD, the address is 0x28 + 2 + 1 = 0x2B. 
This guide was first published on Aug 04, 2019. It was last updated on Aug 04, 2019. This page (Pinouts) was last updated on Sep 18, 2019.